cpufreq: Add a knob to treat IO wait as busy

The new sysfs node io_is_busy enables the interactive governor to
account any time spent by the CPU waiting for IO as non-idle time.
This helps us improve run-time of IO bound tasks by making up for
lost IO time in speeding up the CPU bound parts of the task.

Reviewed on http://git-master/r/#change,86894
cherry picked from 13a15aadc1134b5dae05cdcf9687396644f87411
Signed-off-by: satya popuri <spopuri@nvidia.com>

Reviewed-on: http://git-master/r/89218
Reviewed-by: Satya Popuri <spopuri@nvidia.com>
Tested-by: Satya Popuri <spopuri@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Diwakar Tundlam <dtundlam@nvidia.com>

Conflicts:
	drivers/cpufreq/cpufreq_interactive.c

Change-Id: Ieea68df41cc730535b3572035d1a6f55efb2a86d
1 file changed